Light can be reflected more than once inside a raindrop. Rays escaping
after two reflections make a secondary
bow.

The secondary has a radius of 51º and lies some 9º outside
the primary bow. It is broader, 1.8X the width of the primary, and
its colours are reversed so that the reds of the two bows always
face one another. The secondary has 43% of the total brightness of
the primary but its surface brightness is lower than that because
its light is spread over its greater angular extent. The primary
and secondary are are concentric, sharing the antisolar point for
a center.